Pressure accumulator

ABSTRACT

The invention relates to a pressure accumulator which consists of at least one accumulator housing ( 403 ) with at least one connection ( 411 ) for a pressure medium ( 421 ), especially in the form of a fluid that can be accumulated in the accumulator housing ( 403 ), a filling material ( 419 ) that has hollow chambers or that forms at least one hollow chamber for accommodating at least part of said pressure medium ( 421 ) and/or at least one further pressure medium ( 449 ) being introduced into at least sections of the accumulator housing ( 403 ).

The invention relates to a pressure accumulator consisting of at least one accumulator housing, which has at least one connection for a pressure medium, in particular in the form of a fluid, which can be stored in the accumulator housing, wherein a filling material is introduced at least partially into the accumulator housing, this material having cavities or forming at least one cavity for at least partial accommodation of this pressure medium and/or at least one additional pressure medium.

Pressure accumulators are known in various embodiments in the prior art. For example, DE 20 2007 008 175 U1 discloses a hydropneumatic pressure accumulator or hydraulic accumulator having a movable separation element disposed in an accumulator housing, so that it separates a first working space, preferably a gas space, from a fluid space, as the second working space, and is formed by a diaphragm of a flexible material, in particular an elastomer. At least one housing opening, forming an access to the housing, is provided on the accumulator housing for accommodating and dispensing fluid, in particular in the form of hydraulic fluid.

Pressure accumulators of this type, in particular hydraulic accumulators, are subjected to high demands during operation in hydraulic systems because frequent and intense movements of the elastomeric separation element occur in predefinable operating cycles due to the fluid flowing into and out of the accumulator, thus causing loading and relaxation separately by the separation element with respect to the gas supply in the accumulator, so that overloading and local wrinkling of the material may occur due to shearing stresses on the separation element and may result in tearing, which would fundamentally make the accumulator useless and then the hydraulic system would have to be shut down, at least partially, for replacement purposes. The known pressure accumulators and hydraulic accumulators can be used regularly only as an individual solution for a restricted range of application in hydraulic systems because of their accumulator capacity and/or their damping characteristics, but this leads to a corresponding increase in costs at both the manufacturing end and the consumer end.

DE 197 43 007 A1 describes an accumulator of the pressure accumulator type, having a housing, which has a connection for a pressure medium in the manner of a hydraulic medium that can be stored in the housing. The housing contains a filling agent in the form of one or more hollow bodies filled with a pressure medium which can be compressed when there is a higher pressure prevailing outside of the filling agent.

DE 695 15 899 T2 relates to an energy accumulator, among other things, formed from a rigid outer casing of two parts clamping a separation diaphragm. A heterogeneous structure for accumulation or dissipation of energy, having a capillary porous solid matrix surrounded by a lyophobic liquid is provided in a compartment of the energy accumulator bordered by the separation diaphragm. The compartment is isolated from any contact with another hydraulic fluid.

Against the background of this prior art, the object of the invention is to further improve upon the known pressure accumulators, in particular in the form of hydraulic accumulators, while retaining their advantages, namely to ensure a high accumulator capacity, so that they will have a longer lifetime and can be adapted well to given application fields, based on their damping characteristics and/or accumulator capacity, accordingly, so that various applications are possible with only a few accumulator concepts in order to reduce costs.

According to the invention, this object is achieved by a pressure accumulator having the features of patent claim 1 in its entirety. An important special feature of the invention, accordingly is that, to form a hydraulic accumulator, at least one elastomeric separation element, preferably in the form of a separation diaphragm or a separation bladder, subdivides the accumulator housing into at least two working spaces, one of which accommodates the one pressure medium in the form of a liquid and the other of which accommodates the other pressure medium in the form of a working gas, such as nitrogen gas, and the filling material is bordered or enclosed at least partially by the separation element.

A filling material having cavities and/or forming at least one cavity for at least partial accommodation of this pressure medium and/or at least one additional pressure medium is thus introduced at least partially into the accumulator housing.

The particular advantage of the pressure accumulator according to the invention is that, on flowing into the accumulator housing through the assignable housing opening, the pressure medium that is to be controlled by means of the accumulator and is usually in the form of hydraulic fluid or a working gas in a pneumatic application encounters the filling material that has been introduced into the accumulator housing. Meanwhile, the accumulator housing is filled at least partially with the filling material, so the accumulator capacity of the accumulator for the respective application case can be adjusted in the case of a hydraulic or pneumatic system. Thus, depending on the degree of filling with the filling material, one and the same accumulator, depending on its fundamental accumulator design, can be adapted for a variety of application cases in the aforementioned technical systems. Standardized accumulators can thus be mass produced and filled with different amounts of filling material. This leads to low manufacturing costs because of the benefits of mass production. It is also possible, for the first time, to replace a delivered accumulator with another accumulator filled to a different extent with filling material, so that it is possible to adapt the accumulator to modified specifications of the system even on site, i.e. at the user's end, thus permitting cost reductions for the user's end to this extent.

To be able to adjust the accumulator capacity in the accumulator housing accordingly, the filling material may be introduced as a solid block into the accumulator with a predefinable volume, in particular introducing it by molding or injection molding, wherein the filling material then leaves free a cavity, at least within the accumulator housing, which defines the accumulator capacity of the accumulator, and can be filled with the respective working medium (fluid and/or gas). However, it is especially preferably provided that filling material in the form of a cellular structure is to be introduced into the respective accumulator housing of the pressure accumulator or hydraulic accumulator, wherein the filling material is designed to have cavities, possibly with closed pores, but preferably with open pores in its interior, wherein the individual cavities then communicate primarily with one another through permeable fluid channels accordingly. The more the cavities are then integrated into the filling material and are formed by the filling material itself, the greater the increase in accumulator capacity of the accumulator modified in this way.

The two types of cavity design described above can also be combined with one another.

The cavity volume or hollow compartment volume, which is adjustable and introduced into the accumulator through the filling material, is also suitable for damping the respective medium penetrating accordingly, so that the damping characteristic of the accumulator can also be adjusted to this extent and in particular the stiffness of the damping can be influenced in this way. A further adaptation to predefinable damping characteristics can be achieved if the filling material is designed to be at least partially flexible. A type of spring constant can then be stipulated as a damping constant at the manufacturing end for the respective pressure accumulator in a manner comparable to that with a compression spring.

In a particularly preferred embodiment, if the approach using the filling material according to the invention is used not only for conventional pressure accumulators in the form of gas bottles or other fluid storage bottles for conventional pressure accumulators, but instead is also used for hydraulic accumulators having a movable separation element arrangement, preferably formed from an elastomeric separation material, then the filling material or filling agent introduced into the pressure accumulator may serve to support the separation element, usually in the form of a separation bladder or in the form of a separation diaphragm in its movement. Because of the aforementioned, preferably elastic support by the filling material, overstressing in the separation element material is prevented, as are the negative effects of wrinkling, which thus leads to designs with separation elements having a long service life, which in turn help to significantly increase the useful life or lifetime of the accumulator. Due to the delayed or limited admission of the pressure medium into the respective pressure accumulator, it is thus possible for a homogeneous temperature profile to develop inside the accumulator, which in turn protects the working medium, usually in the form of a hydraulic fluid or a pneumatic medium.

The filling material, with its cavities, is preferably formed from a sintered material and/or a cellular material such as foam, a gel or a woven or nonwoven textile or a comparable textile material. If the filling material inside the pressure accumulator does not need to be elastically flexible, for example, in the implementation of the pressure accumulator as a simple gas or other fluid storage bottle, the filling material may also be made of a sintered ceramic or metallic material or a gelatinous substance, which in a special embodiment can also allow input of the medium to be introduced into the accumulator in the form of a bubble feed, so that the cavities are created within the gel more or less only on the introduction of medium into the accumulator. With a corresponding reduction in the working pressure on the input side of the accumulator, the bubble feed is then released again within the gelatinous substance and the medium that is introduced can be returned to the hydraulic or pneumatic working cycle.

However, with the pronounced elastic characteristic of the filling material, it is advantageous for this to be formed from an open-pore foam, preferably a polyurethane foam. If a textile material is used as the filling material, the textile material, in the form of a supporting structure or a supporting fabric, may serve as a backing for foam components, such as the aforementioned polyurethane foam, for example. On the whole, the filling agent or filling material can basically be used for such structures or substrates that have a high accumulator capacity accordingly, preferably having a sufficient elastic flexibility, and can be introduced well into the internal structure of the accumulator in a permanent and thermally stable form.

In a preferred embodiment of the approach using the pressure accumulator according to the invention, the density of the filling material inside the pressure accumulator can be varied, in particular having a cluster or sandwich-type structure. The respective change in density can preferably be provided in at least one direction of orientation, for example, in the direction of the longitudinal axis of the pressure accumulator. If the filling material is in the form of a foam, then the differences in density can be created by repeated injection or foaming. Thus, for example, a gradient-type design of the foam material would be possible, such that a very dense material is used on the input end of the accumulator and then, with open pores or with a lower density, changes rapidly in the direction of the opposite end of the accumulator housing. Instead of the pressure medium entering into the accumulator housing body, an increased resistance can then be built up in that the barrier property of the foam or some other filling material is increased accordingly. To ensure different densities and cavity structures, it is also possible to provide for different filling materials to be used in some sections in the sense outlined above.

It is advantageous in particular when the one working space contains the pressure medium in the form of a fluid together with the filling material. Much higher pressure energies can be stored in the pressure accumulator with this configuration, if necessary.

More preferably the separation element has the filling material on one of its two sides, preferably on the side adjacent to a pressure medium, which is preferably in the form of a liquid, so that the filling material is at least partially in direct contact with the side of the separation element in that regard. Such contact makes it possible to have a favorable influence on the deformation of the separation element, so that the deformation can be shifted into those regions, resulting in a longer lifetime of the separation element. There is also the possibility of using a corresponding filling material on both sides of the respective separation element, so that the accumulator values and the damping values on the so-called gas side of the accumulator can be influenced. Depending on the design of the accumulator, however, other media can also be separated from one another by means of the respective separation element, for example, separating gas from gas or liquid from liquid. Furthermore, pasty or gelatinous media can also be stored there, depending on the accumulator capacity, and then retrieved from the accumulator cyclically.

The accumulator housing may be in multiple parts, in particular two parts, and the accumulator housing parts that are joined together may secure the separation element in the accumulator housing, such that the one accumulator housing part preferably has at least one connection for the one pressure medium, preferably in the form of a liquid. This arrangement has proven to be especially advantageous to manufacture. The accumulator housing parts may be manufactured as cast parts or as laminates. The separation element may then be disposed between the accumulator housing parts and secured there especially advantageously in welding the accumulator housing parts. By means of an additional connection in the accumulator housing, preferably disposed on the side opposite the first connection, the additional pressure element, preferably in the form of a working gas, may be checked, refilled and placed as needed.

In a further embodiment, the accumulator housing parts can be connected to one another by way of a threaded connection, preferably using a union nut. Meanwhile the accumulator housing may be opened for inspection and repair purposes.

The invention is explained in detail below with reference to exemplary embodiments illustrated in the drawings. In schematic diagrams in the form of a longitudinal section not drawn to scale, they show:

FIG. 1 a first exemplary embodiment of a diaphragm accumulator;

FIG. 2 a second exemplary embodiment of a diaphragm accumulator and

FIG. 3 a bladder accumulator.

FIG. 1 shows a diaphragm accumulator 201. The diaphragm accumulator 201 has an accumulator housing 203 having two rotationally symmetrical accumulator housing parts 205, 207 made of a metallic material. Openings 208, 209, to which connections 211, 213 are welded, are provided in the accumulator housing parts 205, 207. The connection 213, at the top in the plane of the figure, is closed during operation by a removable stopper (not shown) or a screw. A dividing element 215 in the form of a dividing diaphragm made of an elastomer is disposed in the accumulator 203. The separation diaphragm 215 has a peripheral edge bead 217 on its one end. The edge bead 217 of the separation diaphragm 215 is held in a form-fitting manner by a retaining ring 223 and a peripheral groove 225 in the lower accumulator housing part 205. The retaining ring 223 is surrounded by a metal ring 227. At the upper end of the retaining ring 223, a beveled face 229 is formed. Furthermore, the metal ring 227 is inserted into a peripheral groove 231 having recessed outlets 233 at the edge. The metal ring 227 is disposed in the region 235 of the neighboring contact faces 237 of the accumulator housing parts 205, 207 and protects the sensitive dividing diaphragm 215 and the retaining ring 223 from thermal damage and/or welding splashes when welding the accumulator housing parts 205, 207 to one another. A piston-shaped valve body 239 having a central recess 241 on the bottom side 243 is provided in the separation diaphragm 215; in the unloaded state of the diaphragm accumulator 201 shown here, this valve body comes to rest against the fluid-side opening 208 of the lower accumulator housing part 205 to form a seal.

A lower first working space 245, at the bottom in the plane of the figure, for a first pressure medium 221, in particular a fluid such as a hydraulic fluid, is formed by the separation element 215. Above that, there is a second working space 247, which is filled with another pressure medium 249, in particular a gas such as nitrogen (N₂), for example. In addition, there is an elastically compressible filling material 219, in particular an open-pore polyurethane film, in the second working space 249. The filling material 219 supports the separation diaphragm 215 in its movement over the full surface, thereby preventing overloading or wrinkling of the separation diaphragm 215, which could otherwise shorten the lifetime of the separation diaphragm 215.

The cavities and the foam filling material 219 are essentially interconnected, so that the additional pressure medium 249 can diffuse into the filling material 219. The density of the filling material 219 determines how much of the additional pressure medium 249 can be accommodated in the second working space 247. The damping characteristic of the diaphragm accumulator 201 is also partially determined by the compression characteristics of the filling material 219. The damping becomes greater as the rigidity of the filling material 219 is greater. The varying density profile of the filling material 219 is suggested by the different dashes in some sections. In the lower region 251, the density is higher accordingly in order to additionally support the separation diaphragm 215.

In a preferred embodiment of the hydraulic diaphragm accumulator (not shown here), the foam-type filling material may also be filled into individual sandwich-type layers. The density profile, and thus the damping properties, of the foam can be adjusted accurately in this way, in particular in the longitudinal direction LR of the accumulator. Furthermore, a homogeneous temperature profile is also achieved within the accumulator during operation, which protects the media introduced into the accumulator.

FIG. 2 shows another diaphragm accumulator 301. This diaphragm accumulator 301 has an accumulator housing 303 with two accumulator housing parts 305, 307 made of the metallic materials that are generally used for this purpose. However, it is also fundamentally conceivable for one or both of the accumulator housing parts 305, 307 to be manufactured from a plastic laminate. The accumulator housing parts 305, 307 can be joined by a threaded connection 309. To do so, a shoulder 317 is provided on the upper accumulator housing part 307 with a type of clamp ring 323 serving as a union nut being placed on this shoulder. Between a peripheral edge bead 325 of a separation element 315, a separation diaphragm, made of an elastomer here, is held in a form-fitting manner between the accumulator housing parts 305, 307. A valve plate 339 is provided on the separation diaphragm 315; in the unactuated state of the diaphragm accumulator 301 shown here, this valve plate covers an opening 327 in the accumulator housing part 305 at the bottom of the plane of the figure.

A first working space 345 for a first pressure medium 321 in the form of a fluid is formed by the separation diaphragm 315 in the lower accumulator housing part 305. On the opposite side of the separation diaphragm 315, there is a second working space 347, which is filled with a second pressure medium 349 in the form of nitrogen and a filling material 319. The filling material 319 fills the second working space uniformly in the drawing. The filling material 319 in the present case consists of two elastically compressible foam parts 329, 331, which are designed in the form of blocks. The lower foam part 329 has a higher density and thus has a greater damping effect. Due to the fact that the lower foam part 329 is in contact with the separation diaphragm 315, the separation diaphragm 315 is supported in movement and the overstressing or wrinkling that shortens the lifetime is again prevented. The filling material 319 helps to ensure a more homogeneous temperature profile in the diaphragm accumulator 301 during operation. The first pressure medium 321 flowing into the first working space 347 is also protected in this way. An opening 333 in the upper accumulator housing part 307 is provided with an internal thread 335, into which a replacement screw 337 is screwed. This forms a connection 313 which is covered on the outside by a screwed-on cap 341.

FIG. 3 shows a bladder accumulator 401 as an additional approach to a hydraulic accumulator with a separation element. A separation element 415 in the form of an elastomeric separation bladder is disposed in a one-piece bottle-shaped accumulator housing 403, which may also be made of a plastic laminate. The separation bladder 415 in the unactuated state is in the form of a rotational body having a uniform shape. The separation bladder 415 has a reinforcement 407 on one end 405 with a connection 413 incorporated into it and protruding out of the accumulator housing 403, where it is sealed with respect to the outside by a closing stopper 408. A cap 409 is placed on or screwed onto the connection 413. The connection 413 is secured accordingly with a nut 417 on the outside 423 of the accumulator housing 403. In addition, a plate 425 is secured with the nut 417 on the accumulator, which may have an inscription identifying the accumulator and/or manufacturer's information, for example.

A connection 411 with a valve 429 is provided at the other end 427 of the accumulator housing 403. In addition, an accommodating part 433 is disposed on the inside 431 of the accumulator housing 403, centering the part of the connection 411 that protrudes into the accumulator housing 403 and securing it accordingly. The outside wall 435 of the connection 411 is sealed by an 0-ring gasket 437 with respect to the accumulator housing 403. The connection 411 is secured on the outside 423 of the accumulator housing 403 by a centering ring 439 and a nut 441. Supports 451 running transversely are arranged in diametric opposition to one another, relative to the longitudinal axis of the accumulator in the interior 443 of the connection 411, permanently limiting the fluid passage within the connection 411 and accommodating a bushing 453. A rod-type valve body 459, acted upon by a spring 457, is guided through this bushing 453. A valve disk 461 of the valve body 459 protrudes into the interior 463 of the accumulator housing 403, so that the separation bladder 415 acts on the valve disk 461 at maximum extension, so the latter comes into sealing contact with a valve seat 465 of the connection 411 against the action of the compression spring or return spring 457. Furthermore, a screw 467 is provided in the outside wall 435 of the connection 411, such that when it is removed, a corresponding fluid sensor (not shown) can be screwed into that connection 411.

The accumulator housing 405 is again divided by the separation bladder 415 into a first working space 445 for a first pressure medium 421, in particular a fluid, and a second working space 447 situated in the separation bladder 415 for a second pressure medium 449 in the form of nitrogen. The separation bladder 415 is filled by a filling material 419. The filling material 419 is a thermally stable, elastically compressible low-density foam. A plurality of cavities with open pores is provided in the filling material 419. The filling material 419 is in full surface contact with separation bladder 415. The separation bladder 415 is supported in its movement in this way. Overloading of sections of the separation bladder 415 is prevented, along with wrinkling and its negative effects. In addition, the first working space 445 may be formed with an additional filling material, preferably in the form of a fluid-resistant foam, so that the diaphragm 415 can be supported in its movement in two opposite directions of movement during operation of the accumulator.

Meanwhile, the separation bladder 415 has a much longer lifetime than conventional approaches. On the whole, the bladder accumulator 401 according to the invention is therefore characterized by a longer lifetime, a greater accumulator capacity for compression energy and a better damping characteristic. 

1. A pressure accumulator consisting of at least one accumulator housing (203, 303, 403) having at least one connection (211, 311, 411; 213, 313, 413) for a pressure medium (221, 321, 421), in particular in the form of fluid, which can be stored in the accumulator housing (203, 303, 403), wherein a filling material (219, 319, 419) can be introduced at least partially into the accumulator housing (203, 303, 403), said filling material having cavities or forming at least one cavity for at least partial accommodation of a pressure medium (221, 321, 421) and/or at least one additional pressure medium (249, 349, 449), characterized in that at least one elastomeric separation element (215, 315, 415), preferably in the form of a separation diaphragm (215, 315) or a separation bladder (415), subdivides the accumulator housing (203, 303, 403) into at least two working spaces (245, 345, 445, 247, 347, 447), forming a hydraulic accumulator, one of these working spaces (245, 345, 445) accommodating one pressure medium (221, 321, 421), in particular in the form of a liquid, and the other working space (247, 247, 447) accommodating the other pressure medium (249, 349, 449) in the form of a working gas such as nitrogen gas, and the filing material (219, 319, 419) is at least partially limited or enclosed by the separation element (215, 315, 415).
 2. The pressure accumulator according to claim 1, characterized in that the filling material (219, 319, 419), with its cavities, is formed from a sintered material and/or from a cellular material such as a foam (metal foam, polyurethane foam), a gel or a woven or nonwoven textile or a comparable textile material.
 3. The pressure accumulator according to claim 1, characterized in that the filling material (219, 319, 419) is elastically compressible.
 4. The pressure accumulator according to claim 1, characterized in that the density of the filling material (219, 319, 419) varies within the pressure accumulator, in particular having a cluster or sandwich-type design.
 5. The pressure accumulator according to claims 1, characterized in that the separation element (215, 315, 415) has the filling material (219, 319, 419) on one of its two sides, preferably the side adjacent to the additional pressure medium (249, 349, 449), in particular in the form of the working gas, and the filling material is at least partially in direct contact with the side of the separation element (215, 315, 415) in that regard.
 6. The pressure accumulator according to claim 1, characterized in that the accumulator housing (203, 303) is in multiple parts, in particular in two parts; the accumulator housing parts (205, 305; 207, 307), which are joined together, secure the separation element (215, 315) in the accumulator housing (203, 303), and the one accumulator housing part (203, 303) preferably has at least one connection (213, 313) for the additional pressure medium (249, 349), in particular in the form of the working gas
 7. The pressure accumulator according to claim 6, characterized in that the accumulator housing parts (305, 307) can be connected to one another by a threaded connection (309), preferably using a union nut part. 